Linkage-drive pump

ABSTRACT

Apparatus is described for pumping fluids at an elevated pressure, wherein the fluid is monitored and activates a transducer member which in turn adjusts a linkage means for converting reciprocating pumping motion to a transverse oscillatory motion whereby the pumping stroke is controlled to regulate fluid pressure.

[45] Dec. 23, 1975 United States Patent Siczek U.S. Patent 1366.23, 1975 sheet20f4 3,927,605

FIG., 2

U.S. Patent Dec.23, 1975 sheer40f4 3,927,605

LmKAGE-DRIVE PUMP This invention relates to an apparatus ,for pumping, and more particularly' to an apparatus for pumping liquids ata constant pressure, or over a predetermined pressure range. The apparatus of this invention achieves constant pressure pumping by utilizing a pressure-responsive feedback linkage to adjust the pumping stroke of a piston.

In the pumping of liquids, and particularly in the pumping of paint through a paint spray gun, it is important to control and maintain the pressure of the liquid being pumped at a predetermined and relatively constant level. Constant pressure of the liquid paint gives the desirable result of a uniform distribution of paint spray from the paint spray gun, and therefore results in better paint coating applications. The importance of maintaining a relatively constant paint pressure is particularly significant in the airless technique of spraying paint, i.e., where the atomization of the paint liquid is caused by releasing the paint pressure through a very small orifice into the atmosphere. Proper atomization lof paint in this manner is critically dependent on the orifice designl and on the pressure applied to the paint as it is fed into the orifice.

It has been possible to provide relatively constant pressure paint pumping systems in the past, but the cost of such systems has been high enough so that their use has been limited to professional painters and industrial plants where there can be found an economic justification for the investment required. The present invention provides .a relatively simple and inexpensive pumping system which will provide a quality paint coating application at a significantly lower cost than prior art systems and pumps. l

Briefly, the invention comprises a rotary drive mechanism having a shaft preferably rotating at a constant speed. This shaft is connected to a crank and connecting rod assembly for converting rotary shaft motion to reciprocating motion at the connecting rod end. The connecting rod is connected, via suitable bearing connections, to a linkage mechanism which forms a novel and distinct portion of the invention. The linkage mechanism is also connecting, via suitable bearing means, to another connecting rod which `connects to a piston pumping means. The alignment of the linkage mechanism bearing connections is` such as to transfer the reciprocating motion from the drive means connecting rod to the piston pumping means and to thereby cause a reciprocating piston pumping action whenever an increase in fluid pressure is called for. The linkage mechanism is also connected to a pressure transducer and actuating element which monitors fluid pressure and causes motion of the actuating element in response thereto. The movement of the actuating element realigns the linkage mechanism so as to translate the reciprocating motion to a transverse ocillatory motion. This transverse ocillatory motion occurs when no further pressure increase is demanded and results in a reduction of the piston stroke to substantially zero, thereby-causing the piston pumping means to cease its pumping action. The movement of the linkage mechanism from a purely reciprocating motion to a transverse oscillatory motion in response to fluid pressure is continuously variable and adjustable, so as to allow the setting of a preferred operating pressure range for the pumping apparatus` It is therefore an object of this invention to provide an inexpensive pumping apparatus having a pressurecontrolled delivery.

It is another object of this invention to provide a relatively constant pressure pumping apparatus wherein the pressure is controlled by varying the stroke of the pumping piston.

A further object of the invention is to provide a pumping apparatus having a variable stroke piston which is driven by a constant speed motor, and which has a pressure-responsive feedback linkage to control the piston stroke.

These and other objects and advantages of this invention will be apparent from the following specification and claims, and with reference to the drawings, in which:

FIG. 1 is a view of a preferred embodiment of the invention;

FIG. 2 is a diagrammatic view of the various linkages which are employed in the embodiment shown in FIG. 1, under pressure demand conditions;

FIG. 3 is a diagrammatic view of the linkages under a no-pressure demandcondition; and

FIG. 4 is a diagrammatic view of an alternative design for the invention.

Referring rst to FIG. 1, there is shown in side perspective view a preferred embodiment of the invention. A metal housing 10 encloses the operative driving and control components of the invention. Inside of housing 10 is a crank 12 which rotates about a motor shaft 13` and is securely fastened thereto. Motor shaft 13 forms a part of a drive motor (not shown) which is securely bolted to the rear of housing 10. Motor shaft 13 is projected through the rear wall of housing 10 at housing opening 14. Crank 12 has a connecting rod 16 attached at bearing pin 15. The other end of connecting rod 16 is connected to link 20 by means of bearing pin 18. Link 20 is a generally triangular linkage structure which has bearing pins positioned at its respective three corners, for connecting to the movable elements of the invention and for facilitating control over the pump piston 26 stroke. The pump drive rod 22 is connected to the lower bearing pin 2l on link 20; similarly, one end of control arm 24 is connected to another corner of link 20 by means of bearing pin 23. All of these bearing connections are freely movable and rotatable about the respective bearing pins.

The rst end of control arm 24 connects to bearing pin 23 on link 20, and the second end of control arm 24 is pivotally connected to pivot pin 28. Pivot pin 28 is, in

turn, rigidly attached to housing 10. The pivotal motion of control arm 24 about pivot pin 28 is affected by two opposing forces. The first of these is a spring bias caused by spring 30 urging downward on control arm 24; the second of these forces is caused by a pressureresponsive rod 32 which is slidably movable within pressure control housing 35. Rod 32 reacts to pressure variations within delivery line 29, sliding outwardly from pressure control housing 35 on increases in fluid pressure and sliding inwardly within pressure control housing 35 on decreases in fluid pressure. For example, when fluid pressure exceeds the spring force of spring 30 against control arm 24, rod 32 moves outwardly from pressure control housing 35 to pivot control arm 24 about its pivot pin 28. This causes the end of link 20 connected to control arm 24 to move upward and changes the pattern of travel of the connecting rods driven by motor shaft 13. Conversely, when the fluid pressure in delivery line 29 lis less than the spring bias force of spring 30, rod 32 retracts within pressure control housing 35 and allows the spring force to pivot control arm 24 downwardly about its pivot pin 28. This causes the end of link connected to bearing pin 23 to move downwardly and again changes the pattern of motion of the connecting rods driven by motor shaft 13. The respective motion pattern and control thereof will be explained in more detail with reference to FIGS. 2 and 3 hereafter; for present purposes it is suicient to recognize that variations in fluid line pressure cause changes to the pattern and motion of the connecting rods driven by the shaft 13. It will be seen that these motion changes are corrective in nature, and cause an adjustment of line pressure to preserve some constant and predetermined value of line pressure. This fluid line pressure is set by means of the spring force of spring 30 against control arm 24, which can be adjusted initially or during operation by means of adjustment bolt 33. Threading bolt 33 into housing 10 increases the spring force of spring 30 against control arm 24; conversely, threading bolt 33 outward from housing 10 relaxes the spring force. Thus it is possible to select a predetermined pressure, within the pressure limits dictated by the system components, and the pump will automatically adjust its delivery stroke to maintain the pressure constant.

The liquid being pumped with this pump is delivered via outlet connection 36. This liquid outlet is typically connected to a hose or tube for transferring the liquid to its point of use. For example, in the application of the invention for pumping paint to paint sprayers, liquid outlet 36 is connected to a paint hose which, in tum, is connected to a paint spray gun. The hydraulic pressure developed by the pump in the paint delivery lines and hoses provides the force for spraying the paint through the paint spray gun. In a typical application, this hydraulic pressure may range from SOO-5000 psi in the fluid delivery lines.

FIG. 2 illustrates the invention of FIG. l in schematic form. It also illustrates the motion of the pumping apparatus under pressure demand conditions, by showing the position of its relative components in two shaft 13 positions. The component positions will be described relative to the first shaft position situation by reference to the component parts in association with the letter a, and the component positions will be described with reference to its second pressure situation by associating those components with the reference b. Thus, 22a illustrates a pump drive rod position associated with the first shaft 13 position and 22b illustrates a second pump drive rod position associated with the second shaft 13 position. As hereinbefore described, pressure control is maintained by the opposing action of spring 30 against pressure transducer rod 32, and the relative spring force of spring 30 is dictated by the adjustment of adjustment bolt 33.

Pressure transducer rod 32 is activated by means of a pressure transducer, illustrated in FIG. 2 in simple schematic form as a pressure-responsive piston 37 which responds to changes in pressure within delivery line 29. In typical operation any of a number of wellknown pressure transducer devices and techniques may be used to provide the relative motion required by rod 32, including diaphram valves, piston-activated devices, etc. The critical feature of the device shown within pressure control housing 35 is that it provide motion as indicated by arrow 39 in response to changes in pressure within delivery line 29.

If we assume a pressure control position as illustrated in FIG. 2 for control arm 24, which is pivotal about pivot pin 28, then the remaining component positions can be explained with reference thereto. The end of control arm 24 is connected to bearing pin 23. Bearing pins 23, 21a, and 18a, are located within link 20 and therefore have a fixed dimensional relationship relative to one another for any motion configuration of the remaining components. This fixed dimensional relationship is illustrated in FIG. 2 by means of heavy interconnecting lines between the respective bearing pins on link 20. It is to be noted that the position of link 20 is influenced by two factors; the relative position of control arm 24 and the instantaneous position of connecting rod 16 as it is driven by motor 11 via crank 12. Thus, with crank 12a positioned as shown in FIG. 2, bearing pin 15a causes connecting rod 16a to be positioned relative thereto, and bearing pin 18a fixes the instantaneous position of link 20a as a result thereof. In this position, pump drive rod 22a is downwardly moved to cause pump piston 26a to be near the bottom of its stroke.

If motor shaft 13 of motor ll rotates to the second position illustrated in FIG. 2, crank 12b is positioned as shown. Connecting rod 16b is moved by means of its connection to bearing pin 15b, and the two bearing pins 18b and 2lb are moved into the relative position shown. Pump drive rod 22b, connected to bearing pin 2lb, moves upwardly, drawing piston 26b to a position near the top of its stroke. Thus, these examples illustrate how pump piston action is obtained by motor shaft rotation for a rst position of pressure transducer rod 32.

The motion of pump piston 26 as hereinbefore described results in a pumping action, wherein liquid is admitted into the pump cylinder via inlet 27 during the upstroke of piston 26 and this fluid is forced out through delivery line 29 during the downstroke of piston 26. A ball check 40 is illustrated in FIG. 2 to close during the upstroke of piston 26 and thereby retain fluid in delivery line 29 during this upstroke. During the downstroke of piston 26, ball check 40 is lifted from its seat and allows fluid to pass thereby into delivery line 29.

FIG. 3 illustrates in schematic diagram form the same two relative motor shaft 13 positions, but in connection with a second and different pressure transducer-spring configuration. The example of FIG. 3 typifies the pressure control situation wherein fluid pressure in delivery line 29 is at a level corresponding to the pressure demanded by the setting of adjustment bolt 33, and the pump is therefore required to deliver no additional fluid into delivery line 29. It is to be appreciated that the relative movements and positions of the respective system components are exaggerated in FIGS. 2 and 3 for purposes of illustration. The effects described thereby may be equally well obtained in actual practice, but with a great deal less relative motion between components. For example, the amount of spring deflection of spring 30 from a pressure demand situation as illustrated in FIG. 2 to a no-pressure demand situation as illustrated in FIG. 3 is nowhere near the deflection used for illustration purposes in their respective figures. However, some deflection does occur between these two extreme pressure conditions, and by proper selec- Relative to FIG. 3, the component positions associated with the first motor shaft position will be explained in connectionwth the letter c; the component positions associated with the second motor shaft position will be explained relative to d In a first motor shaft position, crank 12e` acts through bearing pin 15C to position connecting rod 16C as shown. The other end of connecting rod 16C locates bearing pin 18e of link 20c. Again, since bearing pins 18C, 21C, and -23 are fixed relative to one another, and also because bearing pin 23 is positioned by the movement of control arm 24, the respective link 2.0 bearing pins are located as shown in FIG. 3. Pump drive rod 22e, connected to bearing pin 21e, is drawn to an upward position and through its connection to-pistonf26 holds piston 26'in'an upward position. It should be noted that the position of control arm 24 is determined by the force of pressure-responsive piston 37, acting through a rod 32, against spring In a second motorshaft position, crank 12d is positioned as shown. Connecting rod 16d causes bearing pin 18 on`crank 20d to move to the position designated as 18d. It should be noted that this position is virtually horizontally displaced from position 18C, and the motion'of link 20 is thereby caused to be essentially a side-to-side motion, transverse to normal pump piston reciprocating motion, in response to the rotation of motor'shaft 13. Since, in this example, control arm 24 remains in a fixed position as dictated by the respective pressuredemand, bearing pin 21d attached to pump drive rod 22d causes thepump drive rod to move laterally. The end of pump drive rod 22d connected to piston 26 has little or no relative upward or downward motion. Therefore, piston 26 does not move in a reciprocating direction and no pumping action occurs.

In summary, the schematic diagrams of FIGS. 2 and 3 illustrate the responsive motion of piston 26 caused by motor shaft 13 rotation for the condition of high` pressure demand (FIG. 2) and also for the condition of low pressure demand (FIG. 3). It is apparent that the pumping stroke under pressure demand conditions is significant, and suicient to deliver fluid through delivery line 29. Conversely, the pumping stroke during low demand conditions is negligible, and no fluid is pumped through delivery line 29.

FIG. 4 illustrates an alternative embodiment of the invention. The pressure-responsive apparatus in this embodiment is arranged and operated in a way slightly different from the embodiment previously described, and the component linkages are also somewhat modified. Fluid pressure in delivery line 29 is sensed by means of a pressure response piston 42 which is slidably actuated within a cylinder 43. As fluid pressure increases, pressure response piston 42 moves upwardly within cylinder 43. This upward movement is transferred by means of pressure rod 44 to spring 30 and produce a force in opposition thereto. Pressure rod 44 is connected to a roller 45, which roller is also connected to a connecting rod 48 by means of a bearing pin 46. Bearing pin 46 and connecting rod 48 are illustrated in respective a and b positions by the designation 46a, 48a, and 46h, 48b, respectively. These positions are indicative of differing motor shaft 13 positions and pressure response piston 42 positions as will be hereinafter described. Connecting rod 48 is connected to a second connecting rod 49 via bearing pin 50. The other end of connecting rod 49 is connected, via bearing pin 51, to crank 52. Each of these components is illustrated in a respective a and b position in FIG. 4, wherein the designation 49a is representative of component 49 in a first a position and the designation 49bis representative of the component in a second b position, which is likewise true of the convention relating to the other components. Similarly, a pump piston drive rod 54 is connected between bearing pin 50 and piston 56. Pump drive rod 54 transmits the verticalcomponent of motion of the other components to move piston 56 up and down.

. The positions illustrated in FIG. 4 by a designators are representative of a pressure demand situation wherein themotor shaft is rotated so as to reciprocate piston S6 over its total possible stroke. As motor shaft 13 rotates under this pressure demand condition, the path of travel of bearing pin 50a, and hence the top end of pump drive rod-54a, is traced by dotted line 60. It can be seen that bearing pin 50a therefore travels between a high point designated as A and a low point designated as C This corresponds to a significant degree of travel and results in piston 56 pumping a large volume of fluid out through cylinder 43 and delivery line29. The vertical travel of piston 56 is correspondingly illustrated by the lines A and C shown adjacentfthe piston. t

The relative component positions designated as b are representativeof a low pressure demand situation and several motor rotation positions. The relative travel of bearing pin 50b asmotor shaft 13 rotates is illustrated by dotted line 61. Since dotted line 6l also represents the travel of the top end of pump drive rod 54b, it can be seen that the relative vertical motion of the pump drive rod is between the lines designated as A and B. This relative motion results in a corresponding shortening of the vertical travel path of piston 56 between lines A and B' shown adjacent 4the piston 56; The position of roller 46b in this example is demonstrative of a high pressure reaction in delivery line 29, wherein pressure response piston 42 has raised' an amount sufcient to cause pressure rod 44 to com press spring 30 upwardly. As has been noted, the result of this pressure response is a shortening of the piston 56 stroke from the distance A-C to the distance A-B. Any

' further shortening of piston stroke will result in a stroke wherein fluid inlet port 57 is never completely covered by piston 56 and there is therefore no pumping action beyond that point. This is true even though piston 56 may reciprocate a distance A-B for if piston 56 does not close inlet port 57 during its downward stroke it cannot develop the pumping pressure necessary to force fluid into delivery line 29.

A ball check 40 is also illustrated in FIG. 4 for the purpose of sealing the fluid delivery path during the upstroke of piston 56. Ball check 40 is forced upwardly to release fluid flow during the downward path of piston 56, at least during that downward portion of piston 56 travel after it has closed inlet port 57.

The foregoing descriptions of embodiments of my invention are representative of preferred constructions, but other forms and variations may be selected by those skilled in the art within the inventive scope as defined in the following claims.

I claim:

1. A fluid pumping apparatus of the type driven by a rotating shaft wherein fluid is delivered at an elevated pressure through a delivery means and fluid pressure is 7 controlled by adjusting the pumping stroke, comprising: v

a. crank and connecting rod means attached to said shaft for translating said rotating shaft motion to reciprocating motion;

b. a pressure transducer connected to said delivery means, said pressure transducer having a movable element which activates in response to pressure in said delivery means, and a pivotal actuating member contacting said movable element, and adjustable spring biasing means contacting said pivotal actuating member for opposing the motion of said movable element;

c. fluid pumping means, connected to said delivery means, for pumping fluid into said delivery means in response to a reciprocating motion drive;

d. a fluid pump connecting rod attached to said fluid pumping means, for imparting reciprocating motion drive thereto; and I e. a triangular link having rst, second, and third bearing connections near respective comers thereof, and having its first bearing connection attached to said connecting rod means, and having its second bearing connection attached to said pressure transducer actuating member, and having its third bearing connection attached to said uid pump connecting rod, said first and third bearing connections being in substantial reciprocating drive alignment when said pressure transducer actuating member is in a rst position, and said first and third bearing connections being in substantial transverse drive alignment when `said pressure transducer actuating member is in a second position. t

2. The apparatus as claimed in claim l wherein said fluid pumping means further comprises a piston connected to said fluid pump connecting rod and a cylinder axially surrounding said piston; a fluid inlet port projecting through said cylinder; and a fluid release port adjacent the end of said cylinder connected to said fluid delivery means.

8 3. The apparatus as claimed in claim 2, further comprising a ball check valve mounted in said fluid release port.

4. A reciprocating piston fluid pump having a variable stroke feature responsive to pressure of pumped fluid in the fluid delivery line, wherein the reciprocating piston drive motion is converted to transverse oscillatory drive motion at a predetermined pressure setting comprising a. a rotating power source having a drive shaft rotating at a substantially constant speed;

b. crank and connecting rod means connected to said drive shaft for converting said rotating motion to either a reciprocating or oscillating motion;

c. a link comprising a rigid body having three pivotal bearings, the first of said bearings being connected to said connecting rod means;

d. a drive rod connected between said link second bearing and said piston;

e. a pressure transducer connected to said fluid delivery line and responsive to fluid pressure changes in said line to cause deflection of a transducer arm;

f. means for connecting said transducer arm to said link third bearing; and

g. pressure setting means connected to said pressure transducer for adjusting the pressure responsiveness of said transducer arm; whereby said link is positioned by said transducer arm to provide reciprocating alignment between said connecting rod means and said drive rod to provide a first piston stroke and said link is positioned by said transducer arm to provide transverse oscillating alignment between said connecting rod means and said drive rod to provide a second piston stroke.

5. The apparatus of claim 4 wherein said pressure setting means further comprises a spring acting against said transducer arm and means for adjusting the force of said spring.

6. Apparatus as claimed in claim 5 wherein said ro- 40 tating power source further comprises an electric motor. 

1. A fluid pumping apparatus of the type driven by a rotating shaft wherein fluid is delivered at an elevated pressure through a delivery means and fluid pressure is controlled by adjusting the pumping stroke, comprising: a. crank and connecting rod means attached to said shaft for translating said rotating shaft motion to reciprocating motion; b. a pressure transducer connected to said delivery means, said pressure transducer having a movable element which activates in response to pressure in said delivery means, and a pivotal actuating member contacting said movable element, and adjustable spring biasing means contacting said pivotal actuating member for opposing the motion of said movable element; c. fluid pumping means, connected to said delivery means, for pumping fluid into said delivery means in response to a reciprocating motion drive; d. a fluid pump connecting rod attached to said fluid pumping means, for imparting reciprocating motion drive thereto; and e. a triangular link having first, second, and third bearing connections near respective corners thereof, and having its first bearing connection attached to said connecting rod means, and having its second bearing connection attached to said pressure transducer actuating member, and having its third bearing connection attached to said fluid pump connecting rod, said first and third bearing connections being in substantial reciprocating drive alignment when said pressure transducer actuating member is in a first position, and said first and third bearing connections being in substantial transverse drive alignment when said pressuRe transducer actuating member is in a second position.
 2. The apparatus as claimed in claim 1 wherein said fluid pumping means further comprises a piston connected to said fluid pump connecting rod and a cylinder axially surrounding said piston; a fluid inlet port projecting through said cylinder; and a fluid release port adjacent the end of said cylinder connected to said fluid delivery means.
 3. The apparatus as claimed in claim 2, further comprising a ball check valve mounted in said fluid release port.
 4. A reciprocating piston fluid pump having a variable stroke feature responsive to pressure of pumped fluid in the fluid delivery line, wherein the reciprocating piston drive motion is converted to transverse oscillatory drive motion at a predetermined pressure setting comprising a. a rotating power source having a drive shaft rotating at a substantially constant speed; b. crank and connecting rod means connected to said drive shaft for converting said rotating motion to either a reciprocating or oscillating motion; c. a link comprising a rigid body having three pivotal bearings, the first of said bearings being connected to said connecting rod means; d. a drive rod connected between said link second bearing and said piston; e. a pressure transducer connected to said fluid delivery line and responsive to fluid pressure changes in said line to cause deflection of a transducer arm; f. means for connecting said transducer arm to said link third bearing; and g. pressure setting means connected to said pressure transducer for adjusting the pressure responsiveness of said transducer arm; whereby said link is positioned by said transducer arm to provide reciprocating alignment between said connecting rod means and said drive rod to provide a first piston stroke and said link is positioned by said transducer arm to provide transverse oscillating alignment between said connecting rod means and said drive rod to provide a second piston stroke.
 5. The apparatus of claim 4 wherein said pressure setting means further comprises a spring acting against said transducer arm and means for adjusting the force of said spring.
 6. Apparatus as claimed in claim 5 wherein said rotating power source further comprises an electric motor. 